This application is based on the application No. 11-86608 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention pertains to an image taking and processing device for a digital camera and to an image processing method used when increasing the number of pixels of image data. It also pertains to a computer readable medium containing a set of computer executable instructions for processing image data.
2. Description of the Related Art
Generally, the resolution of an image captured by a digital camera is improved by increasing the pixel density of the image sensor. However, when the pixel density of the image sensor is increased, the area of each pixel decreases, leading to a deterioration of pixel sensitivity. On the other hand, if the number of pixels is increased without reducing the size of each pixel, the size of the image sensor increases, which increases its cost.
Therefore, a digital camera is known that offers improved resolution by increasing the apparent number of pixels of the image sensor while leaving the size of the image sensor and the pixel density unchanged.
This digital camera is equipped with an operation switch to instruct that the number of pixels be increased, such that when this operation switch is operated, the resolution increases to double the previous value, for example, in response to the operation of the operation switch.
In the prior art, the number of pixels is increased by creating pixel data for interpolation by performing calculation with reference to peripheral pixels, and then performing pixel interpolation using this pixel data.
In addition, the number of pixels is also increased in a limited part of the image by exposing the photo object with a different angle of view and splicing together parts of the multiple images thus obtained while ensuring that the sizes of the images are the same.
However, there are limits to the degree of resolution improvement that may be obtained by means of pixel interpolation via calculation based on peripheral pixels. In particular, in a digital camera having a zoom function, where wide-angle exposure is performed, the photo object frequency components increase, and a higher resolution is required. As a result, the method of performing pixel interpolation through peripheral pixel calculation entails the drawback that the resulting image suffers from reduced reproducibility regarding the details.
The method involving splicing of image parts suffers from the drawback that that seams stand out, causing the image to appear unnatural.
The present invention was created in order to resolve the problems described above. The first object of the present invention is to provide a digital camera in which the number of pixels in the captured image can be increased without changing the size of the image sensor or the pixel density, and which is capable of capturing images that have good reproducibility regarding details and do not have an unnatural feel.
A second object of the present invention is to provide an image processing method by which to obtain high-resolution images having good reproducibility regarding details.
A third object of the present invention is to provide a recording medium to store a program that executes this image processing method on an image processing device such as a computer.
The first object is attained by means of an image taking and processing device for a digital camera, the device comprising: at least one image sensor, having a fixed number of pixels, to output image signals responsive to an image taking operation; a selector to select a quantity of pixels to be used in capturing an image, wherein in a first mode of operation the quantity of pixels is greater than the fixed number of pixels; an image taking lens having zoom functionality; a controller, responsive to instructions from the selector, to control an image taking operation; and an image processor, coupled to the at least one image sensor, to process image signals received from the at least one image sensor, wherein in the first mode of operation, (i) the controller is adapted to change a focal length of the image taking lens subsequent to a first exposure and automatically effect a second exposure of a subject object and (ii) the image processor is adapted to perform pixel interpolation for image data obtained from the first exposure, wherein the image processor is adapted to determine whether corresponding pixel data from image data obtained from the second exposure exists for pixel interpolation position of image data obtained from the first exposure, and when such pixel data exists, the image processor is adapted to incorporate such pixel data from image data obtained from the second exposure into the image data obtained from the first exposure.
Using the device having the construction described above, when pixel data of the image data obtained from the second exposure exists that corresponds to the pixel interpolation positions of the image data obtained from the first exposure, the image processor is adapted to incorporate pixel data from image data obtained from the second exposure into the image data obtained from the first exposure. Consequently, the resolution of the area that undergoes pixel interpolation is improved.
Moreover, because pixels are certain to exist at the pixel interpolation positions of the image data obtained from the first exposure due to pixel interpolation, the unnatural feel that results from an image comprising multiple images spliced together does not occur.
The second object is attained by a method for processing image data comprising the steps of: obtaining first image data representative of an object; obtaining second image data representative of the object, wherein the second image data corresponds to a magnification that differs from that of the first image data; resizing at least one of an effective image size of the first image data and the second image data so as to harmonize the effective image sizes of the first image data and the second image data; identifying pixel interpolation positions within the first image data; searching the second image data for pixel data that corresponds to each identified pixel interpolation position of the first image data, which corresponds to specific pixel data of the second image data, with the specific pixel data of the second image data.
Through this method for processing image data, where pixel data of the second image data exists that corresponds to the pixel interpolation positions within the first image data, pixel interpolation for the first image data is performed using specific pixel data of second image data. As a result, the resolution of the area that undergoes pixel interpolation is improved.
The third object of the present invention is attained by a computer readable medium containing a set of computer executable instructions for processing first image data representative of an object and second image data representative of the object, such second image data corresponding to a magnification that differs from that of the first image data, which executable instructions allow a computer to perform the following steps: resizing at least one of an effective image size of the first image data and the second image data so as to harmonize the effective image sizes of the first image data and the second image data; identifying pixel interpolation positions within the first image data; for each identified pixel interpolation position, searching the second image data for specific pixel data that positionally corresponds to such identified pixel interpolation position; and replacing each pixel interpolation position that corresponds to pixel data of the second image data with positionally corresponding pixel data of the second image data.
Using this computer readable medium, the process described above can be performed by means of an image processing device such as a computer, through which images having improved resolution may be obtained when the number of pixels is increased.